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The galaxy MXDFz4.4 existed just 1.4 billion years after the Big Bang and likely helped clear the way for photon channels across the universe.(Image credit: NASA, ESA, CSA, STScI, Ilias Goovaerts (STScI), Marc Rafelski (STScI, JHU), Anton Koekemoer (STScI); Image Processing: Alyssa Pagan (STScI))
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Astronomers have detected an ancient galaxy shining through the cosmic fog of the early universe, offering an unprecedented view that was previously thought unattainable.
Employing NASA’s Hubble Space Telescope, alongside data from the James Webb Space Telescope (JWST) and the European Southern Observatory’s Very Large Telescope (VLT), researchers identified “ionizing” ultraviolet photons — high-energy light capable of removing electrons from hydrogen atoms — originating from the galaxy known as MXDFz4.4. This marks the earliest observation of its kind, occurring merely 250 million years after a significant cosmic event known as the Epoch of Reionization concluded, as detailed in a study published on June 23 in The Astrophysical Journal.
For numerous centuries following the Big Bang, the expanse between galaxies was permeated by a haze of neutral hydrogen gas, obstructing this particular type of radiation. Over time, energy emitted from the nascent stars and galaxies ionized this gas, dissipating the haze and allowing light to traverse the cosmos unimpeded — a phenomenon scientists are still endeavoring to fully comprehend.
“This was considered unachievable,” stated Ilias Goovaerts, a postdoctoral fellow at the Space Telescope Science Institute (STScI) in Baltimore and the lead author of the new research, in an interview with Live Science. “What is truly remarkable about this galaxy is its ability to penetrate so much of the intergalactic medium [the ionized plasma situated between galaxies]. Being the most distant, it faces the greatest amount of intergalactic medium to traverse.”
The distinctiveness of MXDFz4.4 lies in its combination of size and stellar birth rate. This galaxy is approximately 100 times smaller in area compared to the Milky Way, yet it produces stars at a rate about 10 times faster, concentrating a substantial number of massive, young stars within a compact region. According to Goovaerts, this heightened density facilitates the galaxy’s creation of clear pathways through its surrounding gas, enabling ionizing light to escape both the galaxy and, ultimately, the opaque intergalactic space. The research team estimates that between half and all of the galaxy’s ionizing radiation is successfully escaping.
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The discovery, made in October, occurred somewhat serendipitously. While compiling a funding proposal just days before a critical deadline, Goovaerts reviewed a pre-existing, deep Hubble image to ascertain if any prior investigations had sought this specific signal in that area. Within a couple of hours, he identified a promising indication. “It was extremely rapid, from conceiving the idea to realizing, ‘Okay, there’s something here, and it’s significant’,” Goovaerts remarked. “Our excitement was immediate, but it subsequently took months to refine the findings and determine all the galaxy’s characteristics.”
An illustration depicting the galaxy MXDFz4.4 as it appeared approximately 1.4 billion years after the Big Bang, near the conclusion of the Era of Reionization.
(Image credit: NASA, ESA, Leah Hustak (STScI))
The achievement relied on an exceptionally comprehensive set of observations: an extremely deep Hubble image compiled from 40 hours of data; JWST imagery across multiple wavelengths, utilized to analyze the galaxy’s stars and star-formation trajectory; and one of the most detailed spectra ever captured of a single celestial region, gathered over approximately six days of observation with the VLT’s Multi-Unit Spectroscopic Explorer instrument. This spectrum confirmed the galaxy’s distance by analyzing its Lyman-alpha emission line — functioning as a “hydrogen fingerprint,” or a luminescence emitted by energized hydrogen gas, which astronomers can employ to gauge cosmic distances and time.
Prior to this, no other galaxy from this early epoch had exhibited detectable ionizing light, positioning MXDFz4.4 as unique thus far, according to a statement by study co-author Marc Rafelski, deputy mission head for the Hubble Space Telescope at STScI.
Scientists suggest that vigorous bursts of star formation, such as the one observed in MXDFz4.4, might have played a crucial role in clearing the early universe’s hydrogen haze, and that additional galaxies of this nature are likely yet to be discovered.
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Sourse: www.livescience.com
